In recent years, visual display devices equipped with a high-definition large screen are demanded as displays for televisions and computers. Consequently, display devices such as liquid crystal panels and plasma display panels are remarkably increasing in size.
The reason for this is, for example, a display needs to have a wider angle of view in order to present a more realistic image to the viewer. In quantitative terms, it is known that in order to create a realistic effect such as a stereoscopic effect, visual impact and so on, a display needs to have a horizontal view angle of at least 30° (i.e. ±15°, which denotes that a range of 15° extends from the center to each of the right and the left. The same applies to the following description), and this effect becomes saturated when the angle reaches approximately 120° (±60°).
Therefore, it is desirable that the angle of view is at least 30° and is preferably close to 120° as much as possible. However, to realize a horizontal view angle of 120°, a 200-inch large screen is required at two meters from the viewer, and it is difficult to install such a large screen in a usual living space.
The same is true to immersive displays developed for realizing virtual reality. Since an immersive display has a large display for encompassing the viewer, it is difficult to install an immersive display in a usual living space.
Considering the above, head-mounted display devices (HMDs) are now attracting attention. As disclosed in Patent Literature 1, a head-mounted display device is a small device, but it can provide a high-definition large image, and is applicable to virtual reality technology.